Electric power line is a good medium for data communication as it is ubiquitous to buildings and households in modern cities. However, reliable digital communication must overcome various kinds of noises and interferences presented on the power lines. They are: (1) background noise caused by summation of various low power noise sources, (2) narrow-band interferences, (3) periodic impulse interference with fixed time interval between bursts and (4) aperiodic impulsive interferences. The periodic impulse interference (PII) can further be categorized as Type I interference which is synchronous to the AC power line frequency of either 50 or 60 Hz, and Type II interference that is asynchronous to the AC line frequency. Type I interference is typically caused by dimmers, and rectifier diodes . . . , etc, and is rarely observed in other communication systems. However, the amplitude of the Type I interference can be stronger than the signal and its burst duration can be fairly wide. Thus the useful time interval for data transmission is greatly reduced. Hence a good power line communication device must combat this Type I interference effectively.